Rotatable loop antenna



NV- 10, 1942. w. P. LEAR ETAL ROTATBLE LOOP ANTENNA Filed March 28, 1940 INVENTORS, 'lliam 9? cear 61411113 L01 ylrefg ATTORNEY.

Patented Nov. 10, 1942 y y UNITED rSTATES PATENT OFFICE ROTATABLE LOOP ANTENNA William P. Lear, Dayton, and Arling W. Ryberg,. Murlin Heights, Ohio, assignors, by mesneassignments, to Lear Avia, Inc., Piqua, Ohio, a corporation of Illinois Application March 28 1940, Serial No. 326,454 7 claims. (c1. 25o-a3) 'I'his invention relates to radio directional ansecured thereto with a locking means 20 to be tennae, and more particularly relates to th'e simdescribed hereinafter in connection with Figs. 2 pliflcation of rotatable loop antenna structures. and 4.

It is the principal object of `th'e present inven- Fig. 2 is an enlarged cross-sectional View tion to provide a novel rotatable loop antenna l through the loop assembly base. The metallic of rugged construction with a minimum number tube I0 is welded or brazed to extending neck of parts, The inventioncontemplates a tubular portion II along 2I. The loop winding 22 proper loop section rotatably supported by a depending comprises a suitable number of turns of insuextension in frictional bearing engagement with lated wire, threaded through tube I 0 and surthe base and coupled thereto by spring action. rounded by-solidied Wax 23. Tubular loop I 0 The frictional engagement in the antenna of the is supported on central rod 25, the top portion of invention is arranged as a thrust bearing for the which is pinned to neck II by olf-center pin 26. vertical loop section, and is also designed to be Rod 25 has a central bore 2'I through which the sealed against atmospheric conditions. The loop terminal leads 2B, 29 of loop winding 22 extend. winding is constructed by threading wire through An important feature of the present invention a neck portion of a continuous tubular body, and resides in the compact and structurally simplified is supported in the tubular body by solidied wax arrangement of the loop antenna assembly. which also weath'erproofs the Winding. Central rod 25 bears an extending collar 30, the The foregoing and other objects, features and top surface of which is juxtaposed against neck advantages of the invention will appear in the II, and the bottom surface of which is cupped or following detailed description of specific embodiotherwise conically arranged to coact with coniments thereof, illustrated in the accompanying cal bearing head I1. Conical head Il extends drawing, in which: above the surface of base I2, and is integral with' Fig. 1 is an elevational view of a rotatable loop o a, bushing 3| secured in the vertical opening in antenna embodiment of the invention. 125 base I 2. Conical head II of bushing 3| overlaps Fig. 2 is an enlarged vertical cross-sectional the openings in base I2 to prevent moisture enview taken along the line 2-2 vof Fig. 1 through tering therein. Bushing 3| is DreSS-tted in the the support of the loop antenna. opening of base I2, and accordingly does not ro- Fig, 3 is a disassembled perspective view of the tate. It serves as a bearing for the rotatable streamline supporting base of the antenna. '30 loop I 0 at rod 25 and rotatably supports collar Fig. 4 is an enlarged cross-sectional view 30 on conical head I1. Bushing 3l and its conithrough a modied arrangement for th'e rotatcal head II is preferably of a graphite or oil imable loop antenna, corresponding to a view taken pregnated material, such as graphite impregalong the line a-a in Fig. 2. nated fiber or Bakelite to` constitute a suitable The assembled loop antenna embodiment of 35 bearing surface. the present invention, shown in Fig. 1, comprises Central supporting rod of the embodiment a continuous circular tube I0, having an extendshown in Fig. 2, is made of metal, such as alumiing neck portion II rotatably mounted on base num or alloys thereof. Th'e lower portion of rod I2 in turn secured to a mounting plate I3. The 25 is of reduced diameter, and carries insulation loop Winding is contained Within hollow tube I0, 40 tube 32 on which two spaced slip rings 33, 34 are and is arranged for external connection through supported. Slip rings 33, 34 are press-fitted on slip rings within base I2, to be described. Circuinsulation tub-e 32, and are preferably coated lar tube I0 is of metallic material, preferably with a silver layer for smooth electrical contactlight in weight, such as aluminum or its alloys. ing with the brushes. A transverse hole is drilled The top portion of tube I Il isv split at I4 to 45 throughy rod 25 between slip rings 33, 34, comminimize the elect of eddy current losses. A municating with bore'21. The ends of loop leads varnished fabric or canvas layer I5 surrounds 28, 29 are extended through central bore 2l and split portion I4, to prevent entry of moisture. A said' transverse hole for electrical connection coll-ar 35 in neck portion II rotates on a conical with associated slip rings 33, 34 as shown. Leads bearing surface I1 secured with loop base I2. 50 28, 29 are preferably insulation covered, and

Th'e coaction between collar 30 and bearing I1 their ends are soldered or brazed to edges of slip forms an atmospherically sealed arrangement. rings 33, 34. Rotatable loop I0 is connected with shaft I8 ex- Central supporting rod 25 extends through tending through base I2. The loop I0 is rotatbase I2, and beneath mounting plate I3. Suitable with respect to fixed base I2, and is firmly 575 able bushings 36 and 31 are arranged in the vbote An important aspect of the present invention resides in the simplified assembly of the rotatable loop I on its base I2 by means cfa central rod 25 extending from neck I-I rotatably'7 supported in base I2 by bushings 3I'and 36, and by lock nut 40 on rod 25 pressing against a spring washer 42; permitting rotation of the loop I0 by holding conically cupped collar 30 in frictional bearing relation on conical head I1. A set screw 45 is arranged in nut 40 to lock it onto rod 25 to maintain the assembled condition of the loop intact. I The conical bearing arrangement between collar 3U and head I1 seals this portion of the loop assembly from the atmosphere. As previously mentioned, the split portion I4 of the loop tube I0 is sealed from the atmosphere by fabric covering I5. Loop winding 22 is impregnated with and embedded in moisture-proof wax 23. It is thus seen thatthe antenna structure is well protected from the atmosphere at all possible vulnerable Zones.

External electrical connection to loop winding 22 is afforded through conducting brushes 46, 41 respectively pressed against slip rings 33, 34 by springs 48, 49. The brush assembly is adjustable through screws 50, 5I, and is electrically connected to the exterior by respective leads 52, 53 of loop cable 54. Loop cable 54 passes through an opening in base I2 lined by insulation bushings 55. Brushes 45, 41 and their respective components are insulated with respect to metallic base I2 through insulation linings 5S, 51. The base I2 of the loop is secured to mounting plate I3 by screws 59, 59 across an insulation and weatherproof layer 58.

Access to the brush assembly is readily afforded through a removable base section 60, having a contour continuous with the external surface ofI base I2. Base section 60 is essentially a removable cap arranged to be secured to base I2 proper through screw 6I, as shown in Fig. 2. The overall contour of base I2 and section BD is preferably streamline, as indicated in the perspective Fig. 3. Such streamline contour, when suitably aligned along the direction of travel of the vehicle, reduces the overall aerodynamic resistance of the loop assembly being particularly advantageous when used aboard aircraft. Openings 55 and 5I in base I2 indicate the ready access to the corresponding brush assemblies when cap 60 is disassembled from base I2. The graphite impregnated bushing 3| and its associated conical head I1 are fitted within the vertical opening provided in base I2.

We have found that the loop antenna assembly of the present invention withstands vigorous vibration encountered in any service condition as well as all types of weather conditions, Without deleterious effects. tion occurs between cupped collar 35 and conical head I1, affording a suitable practical rotational support for the rotatable section I5, I I of the loop. The assembly of loop tube I0 and rod 25 against conical bearing I1, and on base by lock nut 40 and A frictional bearing ac- Y integral conical bearing head spring washer 42, permits ready manual rotation of the loop and presents sufficient frictional resistance against rotation to maintain the loop antenna in any angular position to which it is turned. The bearing head I1 serves as a vertical thrust bearing as well. Spring washer 42 suitably spring biases the loop assembly, facilitating the described actions and correlations. Thus, when radio directional bearings are taken on a radio transmitter by manual rotation of the loop antenna through shaft I8, the settings of the loop may be made within small angular tolerances, and the loop will hold its set positions through the frictional forces described. The graphite or oil impregnated bushing 3l and its I1 withstand long periods of service with negligible wear, and seal the interior of the loop assembly from the atmosphere.

Fig. 4 is an enlarged vertical cross-sectional view of a modified construction for the loop antenna assembly according to the present invention, and corresponds to a transverse cross-sectional view as indicated by the line a--a in Fig. 2. The principle of the modified construction of Fig. 4 is similar to that of the embodiment of Fig. 2. The difference resides in that central supporting rod 25 corresponding to rod 25 of Fig. 2 is of insulation material. Such arrangement simplifies the construction, and is preferred where the loop antenna is not subjected to substantial vibrational forces. Like numerals identify equivalent components in Fig. 4 with those of the previous iigures. Central rod 25 is of a strong insulation material, such as fibrous Bakelite. Rod 25 has a metallic sleeve G2 pressfitted onto the top portion thereof. The top end of rod 25 and sleeve B2 are together presstted into extending neck portion II of loop tube I0, and secured thereto by pins 25.

The bearing action between rotatable loop portion Ill and fixed base I2 is constituted by conical head. I1 of impregnated bushing 3l coacting with a cupped or conical portion at the end of neck II. The thrust and frictional bearing action herein is similar to that between shoulder 3D coacting with the conical head I1 in Fig. V2. The slip rings 33', 34 are secured within recesses in insulation rod 25' for coaction with brush assemblies corresponding to those in Fig. 2, but not seen in Fig. 4. The ends of terminal leads 28, 29 of the loop Winding 22 are respectively electrically secured with slip rings 33', 34 by extending through openings drilled upon rod 25.

A bushing 63 is set into the bottom of the vertical opening in base I2 for rotatably supporting sleeve B4 press-tted onto the bottom end of insulation rod 25. A pin 65 further secures rods25 to sleeve B4. Sleeve 64 extends through base plate I3 and has a threaded end portion 4 I corresponding to threads 4I at the end of rod 25. Lock-nut 40 operates on threaded portion 4I to hold the rotatable loop member in proper assembled relationship by exerting sufficient pressure against spring washer 42, for sealing and permitting proper rotatable action of the rotatable loop section on conical bearing head I'I. Loop shaft I8 is inserted into the open end of sleeve 64, and is secured thereto by pin 66 indicated in dotted lines.

The rotatable loop portion containing the loop winding is assembled by threading a proper number of turns 22 in the interior of hollow tube I0, through neck II thereof. The split end I4 of circular tube I0 is then taped-up. Heated liquid wax is poured into tube I through the open neck ll and the sub-assembly is heated to expel entrapped air and properly impregnate the insulation on the Wire 22. During this treatment, the neck portion Il is held upwards to keep the liquid Wax Within the tube. On cooling, the Wax 23 solidies and serves to Wax impregnate the loop Winding 22 and mechanically support the Winding with respect to tube HJ. The tape on split end I4 is then removed, and the nished varnished fabric layer l5 is substituted. The neck Il of the loop is attached to its central tube (or 25'), which in turn is inserted in base l2 and rotatably supported therein by lock nut iii and spring Washer 42 in the manner previously described.

Although we have described and illustrated preferred embodiments of our present invention,

made therein that fall Within the broader spirit and scope thereof, as set forth in the following claims.

What We claim is:

1. A loop antenna comprising a rotatable section containing a loop winding and having an integral extending neck portion and a rod rmly secured to and extending from said neck portion, said rod containing a bore through which the terminals of said Winding extend, a base having ing outside the base, said rotatable section having a portionv directly coacting with and contacting the surface of said head to constitute a frictional thrust bearing and Weather seal.

ing through which said rod extends, a bushing set into said base opening having a conical head extending through the top of said base, and means outside said base and secured to the external end of said rod extending through the to said neck portion containing a bore through which the terminals of said winding extend, a base having an opening through which said rod extends, a bushing set into said base opening having a conical head extending to the top of said base, said extending neck portion having a conical cupped surface coacting With and directly contacting the surface of said conical head to constitute a frictional thrust bearing arrangement and Weather seal therewith, and means secured to the extending end of said rod for holding said tubular section in rotatable relation on said base across said conical surfaces.

5. A loop antenna comprising a rotatable tubular section containing a loop winding and portion, a base having an opening accommodating said rod, a bushing set into said opening having a conical head extending through the top of said base, means outside said base and secured to the external end of said rod extending through the bottom of said base for holding a coacting conical surface of said rotatable section frictionally against the surface of said conical head comprising a nut threaded on said brush means, said base and cap having a continuous streamline contour.

7. A loop antenna comprising a continuous tubular section containing a loop Winding and having an extending neck portion, a rod secured said base and said cap having a continuous streamline contour.

WILLIAM P. LEAR. ARLING W. RYBERG. 

